A Deadly Fall

My CTF map Neighbours features an intell room with a deadly drop. However, I'm looking for a way to make the pit look endless without really enlarging the brush space. Is there a way to do this by fading the black? IE like the tunnels in HL2 did with light? Is there a way to manufacture this effect to make it look like a drop into infinity? Or is it down to lighting solely. Because maybe there's a nifty trick or tip. Also; what about invulnerability? I've got a trigger_hurt set up with FALL damage, plenty of FALL damage. Is 800 plenty enough?

Ah! Thanks nubcake! Dangit I did search. Might as well reference to it; http://forums.tf2maps.net/showthread.php?t=4950&page=2

Otherwise this topic's ripe for the binnin'! Sorry for that.